On "Late Night with Seth Meyers," Jordan explained that he had not one, but three distinct suits to wear on set. There was an ordinary one, a.k.a. the one you see on the posters. There was a light-up one, presumably for scenes in which he had to sport a fiery glow (with digital flames to be added in post-production.)
But there's also a mysterious third suit. Its function? Dunno, but MJB referred to it explicitly as "the naked version."
THE NAKED VERSION.
Curious? Yep, me too. Unfortunately, googling for "human torch naked" does, um, not yield the intended result.